Traffic protection apparatus



Patented July'll, 1950 :County, Pa, assignor to The UnionFSWitch & Signal Gomp any, 'Swissvale, 'fPa., ea corporation A plication April25, 1946, Serial No."664,"780

'4 Claims. (Cl.246-2-19) "My invention relates to traffi-c protection appa --ratus,and particularly to apparatus for providing crossover protection for trains movingalong railway tracks-which-are connected witheach other "by a crossovertrack through handoperatedtrack switches. J

A requisite for vcrossover protection-apparatus 1s that'it -must-be so arranged that'a car or locomotive, while-occupying acrossover such for example as-a crossover connecting two main tracks, while the switches are in the normal posit-ion for "train movements along the --main tracks, will cause a signal "for each main track to indicate 'stop if the car or locomotive is within fouling distance of thatgm'ain track. In crossover protection schemes embodying track circuits, one characteristic, should therefore be high shunting "sensitivity in 'order'to' insure that the crossover trackcircuit will be shun-ted if the crossover track has high contact resistance due to infrequent :trainmovementsoverthe-crossover.

"One feature of my'invention is the provision of two coded'crossover" track circuits, which inherently have higher --sh-unting sensitivity than non-coded track circuits having the same normal "battery voltage. These track-circuits are also so arranged-as to provideprotect'ion against defective insulated rail joints.

"A vfurther feature of -my "invention is an arrangementof decoding circuits such-that the two track'relays require onlyone decoding transformer and one code detectingrelay.

Ishall describe two forms of apparatusem- 'body'ing my invention, and shall then point out the novel featuresthereof in'claims.

In the accompanying drawingsfFig. l is a 'd-ia- -grammatic view showing one'f-orm of apparatus "embodying myinvention, in 'whichthe polarity of the current-supplied to the crossover track 'circuits'isperiodically reversed at a-given code rate; and Figrzisa diagrammatic view showing'a modified'form of the apparatusofl ig. l, in

which-the polarity of the current supplied to the crossover'track circuits is not reversed,'but the current isperiodicallyinterruptedat=a given-code rate.

Similar reference characters refer to similar parts in-eac-h of the views.

Referring-first to Fig. 1, a stretch of -railway is shown comprising two parallel tracks, designated by thereference characters IT'an'd- 2T, connected. with each other by a crossover-track, designated 3T, throug-h hand operated switches I'W "and 2W. 'Irack-S'I is divided-by means of insulated joints-4, into'two sections a- -b an'db-e-c.

--ergizingthe primary Windingof -a decoding trans- 'former F. A condcnser:D=is connected across example, as 180 cycles-per minute; switches- IW .anclIZW are in the normal position asshown in the drawings, andhence relays 'IR a-nd' ZR in -Ii'ig. :1 are being energized by current oiialternately normal and reverse polarityat a frequency serve-as an arc suppressor.

operated by: relayZR, and mechanically rectifies "the current outputfrom the secondary winding'of ztrainsformer Ffor energizing a slow'pick-up and :slow release code detectingrelayRP.

i2 lEachs-of .the sections -ab:"and b-c" is provided with a'track :circuit including a suitable source of current such-as abattery- IQ or 2Q respectively,: connected 'tlirough a variable resistor 5 and pole changingcontacts fi' and H1 ofa coding device l8llCT'across the rails 3a and-3b of track 3T a'd- "jacent the end of its section atthe mid pointb of track 31. Coding device I BUCT is constantly energized by a suitable source of current-having terminals Band N, and-therefore contactse-and 10 of this-device are repeatedly moved toconnect "alternately with their "front and back :points. Z-Ea'ch of these track-circuits also includes a polar 15 stick code *iollowing track relay IR or 2H respec- "switch contacts Jaand 9 operatedbyswitch IW --0r' 2W respectively, across the rails "adjacentthe opposite end of its section.

tively,-connectedthrouglra variableresistor 8 and A polar contact '"l'l is operated by relay lR-"for controlling current -for-repeatedly reversibly enthe'normal and reverse points of contact to A polar conact l4is Signalcontrolcircuits'for tracks'liT and 2T are controlled by contacts l :and' I8, respectively, of relayRP.

i=Referringnow to 'Fig. 2, the apparatus, here shown, di fiiers 'from that if '1- in: that current, instead of being supplied to the track-circuits throughpole changing contacts is controlled by contacts H! of coding device CT,Which periodically interruptsthe current and place'shunts across the rails of the tracksections; code followin grelaysi-IR and ZRare neutral relays; and, in order to simplify the drawing, resistant and switch contacts"! and'9 are omitted.

-.-I-Iav-ing thus described, in general, the arrangementwofthe apparatus I shall now describe, in detail, its operation.

As shown-inthe drawings, all parts are'in-the normal condition, that is, 'contactsli and lfl of "coding device LBUCT shown'in (Land :contacts l9 o'f-coding device'CT shown in Fig.2, are

being repeatedly closed alternately atitheir front and back vpoints at a suitable'frequency such;- for corresponding to that of the coded current bein supplied to the track circuits; relays IR and 2R in Fig. 2 are being successively energized and deenergized at the code frequency; and relay RP is energized by current controlled by contacts of re- 5 lays IR and 2R.

Each time the contacts 6 and ID of coding device IBBCT are closed at their front points, relay IR is energized by current of normal polarity in a circuit passing from the positive terminal of 10 battery IQ, through a variable resistor 5, front point of contact 6, rail 30., contact I of switch' IW closed in the normal position, variable resistor 8, winding of relay IR, contact 9 of switch IW closed in the normal position, rail 3?), and the front point of contact I0 back to the negative terminal of battery IQ. Each time the contacts 6 and III are closed at their back points, relay IR is energized by current of reverse polarity in a circuit which is the same as the normal circuit just traced except that it. includes the back points instead of the front pointsof contacts 6 and III.

Relay 2R is controlled by contacts of coding device IBIICT which are closed at their front and back points at the same times as the contacts of {2 coding-device IBIICT which control relay IR. Relay 2R is therefore energized by current of normal and reverse polarities simultaneously with relay IR.

- Each-time that contact II of relay IR becomes-3 closed in the left-hand position, as shown in the drawings, a current pulse is supplied from positive terminal B of a suitable source of current, to contact II, through portion I2 of the primary winding of transformer F, to negative terminaL- N of the same source of current. Each time that contact I I becomes closed in the right-hand position, a current pulse is supplied by a similar circuit, but in the opposite direction through portion I3 of the primary winding of transformer F;

Since relays IR and 2R are simultaneously energized by current of like polarities, contact I4 oi relay 2R becomes closed in the left-hand position at the same time that contact I I of relay IR becomes closed in the left-hand position, and i5 similarly these contacts become simultaneously closed in their right-hand positions. Contact I4,

connected in the circuit arrangement shown, therefore serves to rectify the current output from the secondary winding I5I 6 of transform- 5U er F for energizing the code detecting relay RP.

Contacts I I and I8 of relay RP are therefore closed in the signal circuits for tracks IT and 2T, respectively;

If*switch IW should be reversed for a train movement over the crossover track 3T, or if section ab should be shunted by a train, relay IR would become deenergized, and would therefore cease to move its contact I I between the right and left-hand positions. One of the portions I2 and I3 of the primary winding of transformer F would therefore remain deenergized, and the other portion could only be energized by steady direct current. The secondary winding of transformer F would therefore be deenergized, and relay RP would also be deenergized and its contacts I! and I8 would open the signal control circuits, causing signals for both tracks IT and 2T to indicate stop.

If switch 2W should be reversed for a train movement over crossover track 3T, or if section b-c should be shunted by a train, relay 2R would become deenergized, and would therefore cease to move its contact I4 between the left and righthand positions. Contact I4 would therefore cease 4 to rectify the secondary current output from transformer F, and hence contacts I! and I8 of relay RP would again open the signal control circuits.

In the arrangement shown in Fig. 2, when the contacts of coding device CT are closed at their front points, relay IR becomes energized by a circuit passing from the positive terminal of battery IQ, through a variable resistor 5, front point of a contact I9 of coding device CT, rail 3a, winding of relay IR, and rail 31) back to the negative terminal of battery IQ. When the contacts of coding device CT open at their front points, battery IQ is disconnected from section a-b, and

when these contacts become closed at their back points, a shunt is placed across rails 3a and 3b,

and hence relay IR becomes deenergized. Relay 2R is controlled similarly to relay IR. Since relays IR and 2R are controlled by contacts of the same coding device CT, contacts 20 and 2I of these relays will be simultaneously closed at their front points, andalso simultaneously closed at their back points.

Transformer F and relay RP of Fig. 2 are controlled by contacts 20 and H similarly to the manner in which transformer F and relay RP are controlled in Fig. 1.

Some of the advantages provided by apparatus embodying my invention are as follows:

i. Fouling protection.A train occupying crossover track 3T at any point within fouling distance of either track IT or 2T will deenergize either relay IR or 2R, which will in turn deenergize relay RP and thereby open the signal control circuits for both tracks IT and 2T.

2. Superior shunting sensiticz'ty.-As has already been stated, coded track circuits inherently have higher shunting sensitivity than non-coded track circuits having the same normal battery voltage.

3. Broken rail protection.All portions of the track rails in crossover track sections (1-?) and b-c are included in the track circuits in series, and hence the best possible broken rail protection is provided.

4. Foreign current protection.A well-recognized feature of coded track circuits is their immunity to foreign currents.

5. Protection a g a i n s t defective insulated ioz'nts.If the insulated joint at a in rail3ashould break down, the track circuit, not shown, for track IT would be deenergized. If the insulated joint at a in rail 3b should break down, track relay IR would be shunted. If the insulated joint in rail 3b at point I) should break down, and if there should be a current leak from rail 3a of section 12-0 to rail Ia of track IT, tending to place batteries IQ and 2Q in series across the rails of track IT, the successive reversalof polarities of the current supplied to rails 3a and 3b would prevent operation of a track relay of track IT by batteries IQ and 2Q. Similarly, if the insulated joint in rail 3a at point I) should break down,'the successive reversal of polarities of the current supplied to rails 3a and 3b would prevent operation of a track relay of track 2T by batteries IQ and 2Q. If the coding device ISDCT should fail to reverse the polarity of the current supplied to the track circuits, relays IR and 2R would cease to move contacts II and I4 between the left and right-hand positions, and hence relay RP would be deenergized and cause the signals for tracks IT and 2T to indicate stop.

Although I have herein shown and described only two forms of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In a traflic protection scheme in which a stretch of railway track is divided into two sections, the combination comprising, a track circuit for each of said sections each including the rails of its section and each supplied with current periodically varied according to a given code and each including a track relay which follows said given code, a contact of each of said track relays each repeatedly closed alternately in a first and a second position while its track relay is following said given code, a decoding transformer, means controlled by the contact of one of said track relays for repeatedly reversibly energizing the primary winding of said transformer, a code detecting relay, means controlled by the contact of the other track relay for rectifying current from the secondary winding of said transformer for energizing said code detecting relay, and signal controlling means controlled by said code detecting relay.

2. In a traffi c protection scheme in which a stretch of railway track is divided into two sections, the combination comprising, a track circuit for each of said sections each including the rails of its section and each supplied with current periodically reversed at a given code rate and each including a polarized code following track relay, a decoding transformer, means controlled by a polar contact of one of said track relays for repeatedly reversibly energizing the primary winding of said transformer, a code detecting relay, means controlled by a polar contact of the other track relay for rectifying current from the secondary winding of said transformer for energizing said code detecting relay, and signal controlling means controlled by said code detecting relay.

3. In a traffic protection scheme in which a stretch of railway track is divided into two sections, the combination comprising, a track circuit for each of said sections each including the rails of its section and each supplied with current periodically interrupted at a given code rate and each including a code following track relay having a front and a back contact point, a decoding transformer, means controlled by the front and back contact points of one of said track relays for repeatedly reversibly energizing the primary winding of said transformer, a code detecting relay, means controlled by the front and back contact points of the other track relay for rectifying current from the secondary winding of said transformer for energizing said code detecting relay, and signal controlling means controlled by said code detecting relay.

4. In a-trafiic protection scheme in which a stretch of railway track is divided into two sections, the combination comprising, a track circuit for each of said sections each including the rails of its section and each supplied with current periodically varied according to a given code and also each including a track relay which follows said given code, a decoding transformer, means controlled by one of said relays for energizing the primary winding of said transformer, means controlled by the other of said relays for rectifying the current output from the secondary winding of said transformer, and traffic controlling means controlled by said rectified current.

FRANK H. NICHOLSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,039,820 McCann et a1 May 5, 1936 2,113,982 Gilson Apr. 12, 1938 2,378,325 Rees June 12, 1945 2,391,985 Langdon Jan. 1, 1946 2,395,664 Ihrig Feb. 26, 1946 

